The plan, clearly, was to run the ball early and often. The Colts’ front seven is undersized, the Patriots’ strength is their offensive line and running backs, and the rainy conditions made it tough to throw the football.

The Patriots’ early touchdown off of Alfonzo Dennard’s interception put them ahead to stay, so it was easy to miss the fact that the running game wasn’t exactly ripping it up at first. The Patriots ran the ball on 21 of their first 31 plays, and on 23 of 30 total first downs. While some were goal line situations, which affected the average, they ran for just 56 yards on the first 16 of those first-down opportunities, an average of 3.5 yards per carry.

But they stuck to their run-first approach, slowly wearing down the Colts’ front seven. Playing from ahead allowed them to stay patient, but they didn’t panic and go pass-wacky, either.

And then finally . . . bang.

LeGarrette Blount broke free for a 73-yard run on the 17th first-down run, putting the Patriots ahead by 14 points early in the fourth quarter. Later in the fourth, Blount ripped off a 30-yard run on first down, followed by a 10-yard run by Stevan Ridley.

By the end of the game, the Patriots had rushed for 184 yards on those 23 first-down carries (an 8.0 average). And the Patriots held the ball for exactly 35 minutes, keeping the ball out of Andrew Luck’s hands.

Sticking with the run also helped sell the play-action. Brady only hit 2 of 7 passes on first down, but they were big ones: a 27-yarder to Julian Edelman and a 53-yarder to Danny Amendola, both off play-action. The pass to Amendola was especially crucial; it got the Patriots off their 12-yard line, put them in scoring position, and helped them push the lead back to 14 points in the third quarter and halt the Colts’ momentum.

Josh McDaniels and Belichick spend all week putting together an offensive game plan. Sticking to it throughout the night, even when it’s not working perfectly at first, is why the Patriots are advancing to the AFC Championship game for the eighth time in 14 years.

Other observations after reviewing the tape:

When the Patriots had the ball . . .

■ Not only did the Patriots run the ball a ton — 46 times, compared with 27 passes — they ran behind the strength of the offensive line. We counted 32 of the 46 runs going either directly up the middle behind center Ryan Wendell, or to the left side behind Logan Mankins and Nate Solder.

Wendell struggled at times handling Colts tackle Ricky Jean Francois (Dan Connolly provided some solid double-team blocks to help him), but Mankins was an absolute animal, whether he was plowing straight ahead, pulling around to the right side, or getting up to the second level. Solder also had the key block on Blount’s second touchdown run, first starting to his left but then pinning back right to seal the back side and let Blount creep through.

The Patriots smartly avoided running much behind right tackle Marcus Cannon, who struggled in both run and pass blocking against Cory Redding and Erik Walden, though he did have a key block on Blount’s 73-yarder. And Solder continued to struggle with the speed rush, getting burned badly by Robert Mathis for a strip-sack in the fourth quarter.

■ The Patriots had a true running back committee, as Blount played 28 snaps and Ridley and Shane Vereen each played 23. Of Blount’s 28 snaps, he carried the ball 24 times. Don’t be shocked if the Patriots run a lot of play-action with him against Denver.

■ Speaking of animals, fullback James Develin and tight end Michael Hoomanawanui deserve special mention, because they were also phenomenal in the run game. Hoomanawanui played 100 percent of the offensive snaps (74) for the first time this season, while Develin was in for 35 plays, his second-highest play count, and both were absolutely crucial in the run game.

Develin was a sledgehammer coming through the hole as the lead blocker, and crushed Darius Butler to pave the way for Blount’s first touchdown. Hoomanwanui struggled a couple times when lined up against Mathis in run blocking and pass protection but otherwise did a great job of sealing the edge and springing Blount.

Blocking tight end Matthew Mulligan, who played a season-high 35 snaps, also performed admirably in the run game.

■ The Colts played a lot of single-high safety and stacked the box with an extra defender, which is why the Patriots’ run game had to grind it out. But the tactic hurt the Colts on Blount’s long touchdown; there was no one back in the second level to stop him once he broke free. And they didn’t really blitz Brady much, sending extra pressure on just 10 of 27 drop-backs. The Patriots’ only key play against the blitz was the pass interference call on Josh Gordy against Edelman.

■ LaRon Landry bit badly
on Brady’s play-fake on the 53-yarder to Amendola. Brady was lucky that he wasn’t intercepted by Antoine Bethea in the end zone in the fourth quarter on just a terrible throw to a tightly covered Edelman. And the Patriots’ offense really hit a lull in the middle of the game before Blount broke free, going three-and-out on four of five possessions. Brady threw seven straight incompletions in a stretch from the third to fourth quarter.

When the Colts had the ball . . .

■ This game was truly a coming-out party for rookie linebacker Jamie Collins, who played sparingly through the first 12 games of the season but played all 65 snaps Saturday as one of Brandon Spikes’s replacements.

Collins, a high school quarterback who began his college career at safety and then converted to a pass rusher, displayed all of his athletic talents and showed why the Patriots drafted him in the second round.

We counted nine blitzes for Collins, and twice he hit Luck to force an incompletion, once forced Luck to throw into the turf, and had an impressive sack, during which he leaped over Donald Brown and essentially landed on Luck.

Collins had an incredible play in the run game where he spun off a defender, hit the ground, and whipped Trent Richardson to the turf with his forearm. And Collins ranged back 20 yards in zone defense in the fourth quarter to easily intercept Luck, who clearly didn’t expect a linebacker to be playing that far back. Just an awesome all-around performance.

■ For all the grief Dont’a Hightower has gotten this season, he was excellent in run coverage, shedding several blockers to lead the team with eight tackles and helping limit the Colts to 69 yards on 21 rushes (3.3 average). And while he’ll never excel in pass coverage, he did come up with his first career interception when the ball bounced off fullback Stanley Havili.

■ The Patriots opened the game in man coverage, with Aqib Talib shadowing T.Y. Hilton (and doing a really nice job of keeping up), but actually dropped into a lot of Cover 3 and Cover 4 throughout the game. Luck was happy to take the underneath routes and slowly chewed up the defense to claw back to 21-15 in the third quarter.

The Patriots were actually in Cover 4 on LaVon Brazill’s 35-yard touchdown in the third quarter. Devin McCourty was just caught flat-footed and let Brazill beat him to the inside.

■ The NFL is in good hands with Luck. Yeah, he threw four interceptions. He also showed an incredible ability to escape the rush and make some impossible throws, like the 46-yarder to Hilton when being crushed by Collins, or the 38-yard touchdown to Brazill in the face of a five-man rush, or the 40-yarder to Hilton off the wrong foot.

The Patriots smartly blitzed Luck on only eight of 45 drop-backs; he’s the rare young quarterback who correctly can diagnose pressure before the snap and find his open receiver.

■ Another game of consistent pressure from Chandler Jones, who owned Anthony Castonzo. Rob Ninkovich was lucky he didn’t get called for a late hit on Luck. And Joe Vellano was especially lucky he didn’t get called for tripping Luck on his third-quarter sack.

Special teams . . .

■ Teams really need to stop giving Edelman returnable punts. We counted 14 tacklers that he avoided on his five punt returners. His teammates call him “Squirrel” for a reason.

■ Unbelievable effort by Stephen Gostkowski, who hit touchbacks on 7 of 8 kickoffs and had an impressive 41.8-yard average on five punts, with a long of 53 and a fair catch. Overall, the Colts returned just 3 of 6 punts for a total of 5 yards. Ryan Allen tried to stay in the game after his injury, booming off a 67-yard safety punt, but he immediately grabbed his shoulder after the kick. Awesome job in kick coverage by Matthew Slater and Kanorris Davis.

■ We’ll give Danny Aiken a pass on the bad snap that led to a safety. But the Patriots had four special teams penalties for 35 yards, which is unacceptable.

Game balls

■ RB LeGarrette Blount. Let’s hope he hopped in the cold tub Saturday, for as many times as he slammed into the line of scrimmage.

■ FB James Develin and TE Michael Hoomanawanui. The unsung heroes of the Patriots’ dominant run game.

■ LG Logan Mankins. Always plays to the whistle and is still one of the nastiest offensive linemen in the game.

■ LB Jamie Collins. Had the game of his life, and will have to duplicate it against Peyton Manning and the Broncos.

■ CB Alfonzo Dennard. Had two interceptions, the first of which gave the Patriots an early lead they never relinquished.

BostonGlobe.com complimentary digital access has been provided to you, without a subscription, for free starting today and ending in 14 days. After the free trial period, your free BostonGlobe.com digital access will stop immediately unless you sign up for BostonGlobe.com digital subscription. Current print and digital subscribers are not eligible for the free trial.

Thanks & Welcome to Globe.com

You now have unlimited access for the next two weeks.

BostonGlobe.com complimentary digital access has been provided to you, without a subscription, for free starting today and ending in 14 days. After the free trial period, your free BostonGlobe.com digital access will stop immediately unless you sign up for BostonGlobe.com digital subscription. Current print and digital subscribers are not eligible for the free trial.